An image forming apparatus has been considered, which is provided with a plurality of image carriers on which latent images according to image data respectively corresponding to different colors is formed, a plurality of development sections which respectively develop the latent images formed on the image carriers using development agents having different colors, and a transfer section for superimposing and transferring the development agents which develop the latent images formed on the image carriers on a sheet. In the image forming apparatus of this kind, there are provided an image carrier such as a photoconductor drum for each color such as yellow, magenta, cyan and black, and a development section such as a development roller. On the image carrier, an electrostatic latent image according to the imaged at a corresponding to each color is formed. The electrostatic latent image corresponding to each color is developed by the development agent having each color by the development section. Thus, the development agent having each color which develops the electrostatic latent image corresponding to each color is superimposed and transferred on a media to be recorded such as a sheet by the transfer section, thereby forming a multicolor image on the sheet.
In the image forming apparatus of this kind, in all cases, the image is not formed using the development agents having all colors. For example, the monochrome image may be formed using only some development agents such as only black. Thus, JP-A-2004-170654 discloses that, when the monochrome image is formed, the stopping of the development roller corresponding to colors other than black. Thereby, the degradation or depletion of the development agent of the colors other than black can be suppressed.
Herein, it is considered to be judged whether the monochrome image or the color image is formed, based on data of a header or the like attached in transmitting the image data from a personal computer (herein after, referred to as a “PC”) as a higher-level apparatus to the image forming apparatus. However, when a user instructs color printing using a printer driver of the PC even if the image data is monochrome, data for forming the color image is attached to the image data. Then, the image carriers and development sections corresponding to all colors are driven, and as described above, the degradation or depletion of the development agents having colors other than black cannot be suppressed.
All the input image data are analyzed without referring to data such as the header, and it is also considered that the image formation is started based on the analysis result. In this case, prior to the image formation, it can be correctly known by the analysis whether the image data is monochrome. However, when starting the image formation after analyzing all the input image data each time, the time required for the image formation becomes too long, which is not practical.